Chart reading and recording apparatus



United States Patent 3,328,801 CHART READING AND RECORDING APPARATUSArchibald Raymond Boyle and Donald Alfred Dobbin, both of Glasgow,Scotland, assignors t0 D-Mac Limited, Glasgow, Scotland Continuation ofapplication Ser. No. 328,370, Dec. 5, 1963. This application May 25,1966, Ser, No. 559,656 Claims priority, application Great Britain, Dec.6, 1962, 46,059/62 5 Claims. (Cl. 346-31) This application is acontinuation of copending application Ser. No. 328,370, filed Dec. 5,1963, now abandoned.

This invention relates to apparatus for reading and recording positionsand/ or the shapes of lines on a chart, map, diagram, drawing, plan orthe like (hereinafter and in the claims referred to simply as a chart).

It is an object of the present invention to provide apparatus forreading and recording position and/or the shapes of lines on a chartwhich apparatus is simple to operate and accurate in use, and whichsupplies the chart information as a suitable form for re-transmission orfor conversion into another form, for example a digital form.

The present invention is apparatus for reading and recording positionsand/or the shapes of lines on a chart comprising a manually movableindex, sensing means coacting with said index to produce a signaldependent on the relative position of index and sensing means, meansemploying said signal to control the sensing means and move them in suchmanner as to bring said signal to a predetermined value and meansrecording in sequentially reproducible manner the motion of the sensingmeans.

The present invention is also apparatus for reading and recordingpositions and/ or the shapes of lines on a chart the apparatuscomprising a manually-operable magnetic device for indicating positionsand/ or following lines on a chart, sensing means for disposition on theother side of the chart from said magnetic device and for producing adifferential signal in accordance with relative movement between saidmagnetic device and sensing means, a servo-mechanism operably associatedwith the sensing means and operable dependent on said differentialsignal to effect movement of the sensing means to reduce saiddifferential signal, and means operable by output signals from theservo-mechanism to produce a record of the chart readings.

Preferably, the apparatus includes means for indicating when the sensingmeans is locked-on the magnetic device, i.e. when the sensing means andmagnetic device are in alignment, at which state the output signal maybe recorded by the recording means.

The magnetic device may be in the form of a member of high magneticsusceptibility energised by a coil fed from an alternating supply.Alternatively the device is in the form of a permanent magnet, or in theform of a disc having crosswires on its upper surface and a control coilburied within same. An important feature of the invention is that thedevice is held freely in the users hand without restraint, for examplemechanical linkages, pantographs or the like.

The servo-mechanism preferably comprises a servodriven gantry andtrolley arrangement operating in X and Y axes and carrying the sensingmeans.

The output to the recording means may be in digital form or analogueform from digitisers, potentiometers or other suitable means.

While reference is made to magnetic sensing it will be appreciated thatany other suitable form of sensing can be employed; for exampleinductive, electrostatic, capacitive, optical or radiation.

An embodiment of the present invention will now be described withreference to the accompanying drawing which is a block circuit diagramof the apparatus according to the present invention.

The chart (not shown) is placed face upwards on a table 14 or otherhorizontal fiat supporting surface.

The apparatus comprises a servo-mechanism 11 including servo-drivengantry and trolley arrangement (not shown) operating in X and Y axesmounted beneath the table surface. The trolley which is driven in eachaxis by a motor 12 carries a sensing means comprising two sensers orcoils 13, in each axis. The servo-mechanism also includesservo-amplifiers 14 operated by the sensers or coils 13.

A magnetic device 15 is disposed above the chart, i.e. above the table10, and comprises a suitably shaped piece of material of high magneticsusceptibility energized by a coil 16 fed from a low voltage alternatingsupply 17, via very light leads 18. The device, when in use, is heldfreely in the hand of the operator.

The servo-mechanism operates an output means, for example a digitiser 19which gives the output information in digital form to the recorder 20via a decoder and store unit 21 and an output serialiser 22, and inanalogue form via the potentiometers 30 to a conventional X-Y recorder31. The output information may be recorded by the recorder 26 on punchedtape, magnetic tape or punched cards, and it may be transmitted toanother, possibly remote, location in either the digital or analogueforms.

Indicating means, such as a lamp (not shown) is in circuit with themagnetic device 15 and sensing means 13 to inform the operator whenthese two components are in locked-on relationship. By this is meantthat condition in which magnetic device 15 is directly above the sensingmeans 13 so that the circuit is balanced.

A suitable switch 23 is provided to permit output from the outputserialiser 22 to the recorder 20 only when the magnetic device 15 andsensing means 13 are in lockedon relationship. This switch 23 may bemanually or pedal operated, or it may be a pressure pad associated withthe magnetic device 15.

In use, the operator places the magnetic device 15 on a line on thechart and the servo-mechanism 11 moves to the locked-on position, thisbeing indicated by illumination of the lamp. The operator then moves themagnetic device 15 along the line. This creates differential signals inthe sensing means 13, which signals are transmitted to theservo-mechanism 11 to drive the trolley and the sensing means 13 along aline corresponding to that being traced by the magnetic device 15.Simultaneously, outputs from the servo-mechanism 11 operate therecording means to produce the necessary record of chart information.

In modification, the magnetic device 15 is a permanent magnet while thesensing means consists of symmetrically disposed sensers or coils.

In another modification when using the device with an externalprojection system to read a projected image, the magnetic device is asmall white square or disc of suitable material with crosswires markedon its upper surface, and the control coil 16 buried within same. Thisdisc can be moved manually and easily about the reading surface by theoperator and the projected image is always clearly visible on its uppersurface. Due to the flat nature of the disc no tilting can occur andtherefore no error can occur in positioning.

The sensing means may consist of five coils or sensors. The energisingcoil need not be in the follower disc but may be placed equidistant fromthe four sensing coils.

The disc in this instance may consist of a piece of magnetic materialwithout any attached leads.

It will be appreciated that if the magnetic device is disposed betweentwo sensors (e.g. pole pieces on which pick up coils are wound) then thevoltages produced in the coils will be balanced when the point of thedevice is equidistant relative to the sensors. The resultant voltagescan be compared, amplified and used to drive the servomechanism so as toposition the coils equidistant from the point of the device.

In this way, the point of the device does not have to be directlybetween the coils but can be on an axial line some distance above thecoils. This enables the servo-mechanism to be some distance below thedevice point and certain materials can be interposed in this space toact as a support for the chart, e.g. perspex.

It is to be noted that movement of the sensing head towards thelocked-on position may occur from a position well outside the area ofthe sensing means itself, movement being dependent on the diflerencevoltage generated in the two sensing coils due to the difference indistance between the sensing coils and the energizing coil. It is notnecessary for the operator to place the trolley in the correct positionsince this will automatically occur.

The apparatus may be used to output continuous line information, inwhich case the parameter deciding when an output has to be made isusually time, i.e. a certain number of output co-ordinates per second.The output may, of course, be controlled by any other suitableparameter, for example, a reading of the X-axis can be effected everytime the tens digit of the Y-axis changes. In this embodiment a timingunit 32 is used to control the output of the serialiser 22,. This isparticularly important as it enables the more dimcult part of thecurve-ones which normally would be followed more slowly by theoperator-to possess a larger amount of co-ordinate information percentimeter.

Alternatively, the operator can press a switch every time he passes aparticular point at which a readout is desired. Any output device suchas paper tape punch, card punch and typewriter requires a finite time tooutput a position co-ordinate and for this reason the digitiser issampled by a very short pulse, and the digital information frozen in thestore until output has been completed. It is an important feature of thepresent invention that he can lift the magnetic device 15 to somedistance when moving in between such positions. An automatic switch orthe like (not shown) may be arranged on the reading surface to outputinformation only when the device 15 is pressed on to the surface.

It is to be noted that while the magnetic device can be held quitefreely in the hand when difiicult shapes have to be followed, whenstraight lines or simple curves have to be drawn, the device can beplaced against a ruler or curve to help in smoothness of generation.

The output at the serializer 22 normally appears in the form of X and Yco-ordinates. When producing the line from the recorded output, theaccuracy of the line information mainly depends on the distance apart ofthe points selected, i.e. the time interval and this to some extentcontrols the speed of line reading or writing.

The output would normally be on to punched tape or punched cards ormagnetic tape. The other parameter which must be taken into account isthe speed of the output device. For example, with a simple card punch ortape punch lines must either be followed very slowly or coordinates canonly be output at relatively large distances apart. This is satisfactoryfor meteorological information where points 1 cm. apart can givesufficient accuracy. However, for high accuracy work unless the speed ofreading is to be severely curtailed it is necessary to output on to ahigh speed reading device such as magnetic tape.

The apparatus can also transmit its output information to anotherapparatus which can be operated at some distance from the first. In bothcases, accuracies of the order 0.1% or better can be obtained.

Many different sizes of apparatus can be made to suit the convenience ofthe operator and the size of char-ts to be examined. For the highestaccuracies with large areas it is best to divide the main area intosmall areas, for example 20 cm. x 20 cm.

The apparatus may be applied to the reading of information from stripcharts. This is particularly useful if the chart is a complicatedmultichannel one involving considerable selection by the operator. Hecan merely point the device to the correct trace and the operator canmove the chant past the reading position by a variable speed controlpossibly under foot operation.

Retransmission of information is an important feature of the presentinvention. One apparatus can be used as a drawing device and otherapparatus as a repeater. It is possible also for the receiver apparatusto be arranged as reading or writing apparatus. Thus, if one apparatussends out a drawing which is repeated in selected receivers, any ofthese receivers can add information to the drawing and this can berepeated on all other apparatus including the original.

It should be noted that the apparatus can be employed as a reading unitif lines are already drawn but have to be followed and as a writing unitif the lines are drawn and followed at the same time.

It should be noted that instead of X and Y movement of the sensing headwhich gives Cartesian co-ordinate output, the sensing head movement maybe angular and radial to give polar co-ordinate movement.

A subsidiary turntable may be carried on the sensing head and therotational position of the turntable may be read out through the normalX-Y output. In this instance, a subsidiary energizing coil may be fittedto the white disc or magnetic pencil so that rotation of disc or. pencilcauses the turntable to rotate. By this means it is possible todetermine the attitude of a component.

This arrangement is self-centering and can pick-up a radial angle.

If magnetic sensing is employed in both engaging coils then differentfrequencies are used. Alternatively, different forms of sensing areemployed.

Reference to lines herein should be construed as including letters,digits, symbols and the like.

A suitable gantry and trolley arrangement consists of a gantry extendinglongitudinally of the table or supporting surface and movabletransversely relative thereto, and a trolley, which carries the sensinghead, movable along the gantry.

What is claimed is:

1. Apparatus for reading and recording positions and/ or the shapes oflines on a chart, the apparatus comprising a manually operable magneticdevice for indicating positions and/ or following lines on a chart,sensing means for disposition on the other side of the chart from saidmagnetic device and for producing a differential signal in accordancewith the relative position of said magnetic device and sensing means, aservo-mechanism operably associated with the sensing means and operablein response to said differential signal to effect movement of thesensing means in a direction to reduce said differential signal, saidservo-mechanism including a gantry and trolley arrangement electricallyoperable in X and Y axes and carrying the sensing means, and meansoperable by output signals from the servo-mechanism to produce a recordof the movement of the sensing means.

2. Apparatus for reading and recording positions and/ or the shapes oflines on a chart, the apparatus comprising a manually operable mgneticdevice for indicating positions and/ or following lines on a chart, themagnetic device being a member of high magnetic susceptibility and acoil fed from an alternating current supply, said member beingenergizable by said coil, sensing means for disposition on the otherside of the chart from said magnetic device and for producing adifferential signal in accordance with the relative position of saidmagnetic device and sensing means, a servo-mechanism operably associatedwith the sensing means and operable in response to said differentialsignal to elfect movement of the sensing means in a direction to reducesaid differential signal, and means operable by output signals from theservo-mechanism to produce a record of the movement of the sensingmeans.

3. Apparatus for reading and recording positions and/ or the shapes oflines on a chart, comprising magnetic sensing means having primary andsecondary coils, a manually movable index on which the primary coil ismeant ed for free movement in any direction relative to the secondarycoil in a first plane, means mounting the secondary coil for movement inany direction in a second plane parallel to said first plane, means forproducing a signal that varies with the distance between said primaryand secondary coils, means responsive to said signal to move thesecondary coil in said second plane in a direction to reduce saiddistance, and means for recording the motion of said secondary coil.

4. Apparatus as claimed in claim 3, and means for indicating when theprimary and secondary coils are at a minimum distance from each other,and means operable upon the attainment of said minimum distance toactuate Said recording means.

5. Apparatus as claimed in claim 3, said moving means comprising agantry and trolley arrangement electrically operable in X and Y axes andcarrying the secondary coil.

References Cited UNITED STATES PATENTS 2,679,620 5/1954 Berry 318192,835,858 5/1958 Moseley 318-31 2,871,432 1/1959 Marzetta 318313,140,911 7/1964 Johnson 34631 RICHARD B. WILKINSON, Primary Examiner.

STEPHEN J. TOMSKY, Examiner.

J. W. HARTARY, Assistant Examiner.

1. APPARATUS FOR READING AND RECORDING POSITIONS AND/ OR THE SHAPES OFLINES ON A CHART, THE APPARATUS COMPRISING A MANUALLY OPERABLE MAGNETICDEVICE FOR INDICATING POSITIONS AND/OR FOLLOWING LINES ON A CHART,SENSING MEANS FOR DISPOSITION ON THE OTHER SIDE OF THE CHART FROM SAIDMAGNETIC DEVICE AND FOR PRODUCING A DIFFERENTIAL SIGNAL IN ACCORDANCEWITH THE RELATIVE POSITION OF SAID MAGNETIC DEVICE AND SENSING MEANS, ASERVO-MECHANISM OPERABLY ASSOCIATED WITH THE SENSING MEANS AND OPERABLEIN RESPONSE TO SAID DIFFERENTIAL SIGNAL TO EFFECT MOVEMENT OF THESENSING MEANS IN A DIRECTION TO REDUCE SAID DIFFERENTIAL SIGNAL, SAIDSERVO-MECHANISM INCLUDING A GANTRY AND TROLLEY ARRANGEMENT ELECTRICALLYOPERABLE IN X AND Y AXES AND CARRYING THE SENSING MEANS, AND MEANSOPERABLE BY OUTPUT SIGNALS FROM THE SERVO-MECHANISM TO PRODUCE A RECORDOF THE MOVEMENT OF THE SENSING MEANS.